package cn.cjp.m3d21;

public class Zi3 {

    public Zi3(int num) {
        this.num = num;
    }

    public Zi3() {
        this.num =2;
    }

    //final修饰成员变量,没有直接赋值就必须构造方法赋值
    private final int num ;
}
